adlai

Playing around with a nuVinci hub I picked up, darn thing is really really heavy.

So, as the question asks, is a hub this heavy better suited for a larger 700c wheel, or for smaller wheels, 26" or less?

jowilson

Heavy IGH hub is redundant. Hubs are almost never made to fit certain sizes of wheels. Heaviness of a hub doesn't determine anything at all, it just means the hub is heavy.

rhenning

I suspect if you took the full drive train off a similar geared bike and weighted all the components you would fins there isn't as much difference as you think. IGH get rid of 2 derailluers, part of a chain one shifter and its cable and stops, and probably a few other bits and pieces. If you are weight weenie don't ise one. Roger

Looigi

Regardless of wheel size, it has to support the weight of the bike and the rider. Hub weight is just a small part of that total.

HillRider

Wheel size is immaterial as long as the gearing is chosen appropriately. Hub weight is just hub weight. BTW, the nuVinci is so heavy (2450 grams, 5.4 pounds, as advertised) that losing the derailleurs and one shifter doesn't begin to compensate so don't even consider it if you want a really light bike.

fietsbob

I see them put in 349_16" Bike Friday Tikits, and 26" fat bikes By the bike companies .

Say no better, just an application to suit a chosen purpose ..

sprocket choices will determine where the gear range lies , the 1:1 is in the hub when the control is centered..


If freewheel/cog on hub is same size , smaller the wheel the bigger the chainring..

FBinNY 

If when asking about wheel size, you're thinking about rotational inertia, the hub is always at the center so that doesn't change. OTOH there are subtle differences.

1- the larger the wheel, the slower the rotating speed, so that would argue for larger wheels
2- the larger the wheel, the higher the torque loads within the hub, so that would argue smaller.

Neither is enough to be a deciding factor in any way, so decide based on your overall preference regarding the bike as a whole.

But, if you're in a very hilly area, and plan to push the limit for input gear ratio (chainring/rear sprocket), the smaller wheel will effectively give you the lower gearing without doing so. Here the benefit of lower internal torque could be meaningful. This could make a big difference if you're also very heavy.

adlai

Yes, I've been thinking along the lines you outlined.

It seems to me that large wheels are really useful for when you want to coast on relatively flat areas, because they seem to preserve momentum better than smaller wheels.

But for more varied riding, a smaller wheel might be better because it...should be easier to start from a standstill.

I wonder how a mountain bike could take say...24 inch wheels. The only problem likely would be the crank hitting the ground.

FBinNY 

You misread, or chose to selectively read my comment about momentum.

As I said, the difference wasn't enough to consider a factor. This becomes obvious if you consider the difference in momentum, as compared to the total momentum of the bicycle and rider. So we're talking about something on the order of 1% or so. However, with a heavy hub, smaller wheels mean faster rotation, so that works against you, not for you.

The reason that larger wheeled bikes seem to have more rolling momentum is because the larger wheel has a more favorable strike angle on bumps. If you split the vectors when a wheel strikes a bump of any given size, you immediately see that the larger the wheel the smaller the rearward vector.

Take this to an extreme and compare a bicycle to a skateboard. Both hit a 1.5" step climbing a driveway. The bicycle rolls over it with a minor jolt, but the step is a wall to the skateboard which stops dead and throws the rider off. So, in the real world of roads that aren't railroad tracks, bigger wheels roll easier.

As I said, the ONLY consideration that would make smaller wheels better, is the torque consideration based on gearing, weight and terrain. Otherwise (despite claims to the contrary) bigger IS better.

dabac

There are a couple of DH rigs that use 24" wheels b/c of strength. But those frames are made accordingly, and cranking isn't that big in DH-ing.
They're too heavy to use for a valid comparison anyhow.